Turbulence, Disturbed Flow, and Vascular Endothelium

Abstract

In a series of recent experiments, we have measured striking differences between cultured endothelial cells subjected to laminar flow and cells subjected to turbulent flow. In steady laminar flow, as well as laminar flow oscillated at frequencies up to 1 Hz, there is no evidence of increased cell turnover compared to static controls even though the cells undergo significant realignment in a period of 24 hours. With turbulent flow that contains a broad spectrum of higher-frequency small-scale oscillations, the most visible endothelial cell response is increased mitosis. This cell division occurs at time-average shear stresses as much as a factor of 5 smaller than the steady laminar shear stress required to cause alignment. One possible mechanism for this behavior is discussed.